Excess fluid buildup (edema) in a patient may be associated with many diseases. Edema results from inadequate or excessive response of homeostatic processes in the body. For example, acute pulmonary edema is a short-term fluid buildup in the lungs. In some people, such excess fluid buildup (also referred to as “decompensation”) results from inadequate cardiac output of the heart, such as is associated with congestive heart failure (CHF). Pulmonary edema may occur late in the CHF disease process and may have serious consequences. The fluid accumulation in the lungs may result in labored breathing and, in severe cases, may even result in death. For these and other reasons, there is a need to detect edema.